macvtap direct

[Laine Stump]

On 5/13/20 12:52 AM, Subhendu Ghosh wrote:
> Hi
> 
> Couple of questions around macvtap direct usage:
> 
> 1) is the document here current?
> https://libvirt.org/formatnetwork.html#examplesDirect

Yes. None of that has changed in any major way in many years.

> 
> I have been able to get host to guest network traffic without any 
> special configuration or switch since Fedora 28 when I first started 
> using it. Using <forward mode=vepa> requires switch port mirroring, but 
> just using <forward mode=bridge> doesn't.


If that is the case, then either your guest and host have a secondary 
network connection, or your switch is mirroring traffic and you just 
didn't know about it. The inability to do direct host<->guest 
communication is inherent in the design of macvtap interfaces.


> 
> 2) do any of the language libraries make assumptions that libvirt 
> networks must have a <bridge name=xx> attribute? Foreman's Ruby 
> interface to libvirt errors out with attempting to build a VM on a KVM 
> host with a network defined with <forward mode=bridge>
> https://projects.theforeman.org/issues/25890

The 2nd line in the log attached to that issue report says this:

 >Call to virNetworkGetBridgeName failed: internal error: network 
'macvtap-net' does not have a bridge name.

So, your application (or whatever this "Foreman's Ruby interface to 
libvirt" is) has called virNetworkGetBridgeName() (whatever it's called 
in the Ruby bindings), and since you have a macvtap network, which has 
no bridge device, libvirt sent back an error. You need to find whatever 
in your code is calling virNetworkGetBridgeName().